TiOx-based synaptic memory device for neuromorphic application

• Main Authors: Chang, Lung-Yu, 張容瑜
• Other Authors: Tseng, Tseung-Yuen
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/tq7dfd

碩士 === 國立交通大學 === 電子研究所 === 107 === Neuromorphic computing is expected to emulate brain functions in the near future. There are several nonvolatile memory such as PCRAM, CBRAM, RRAM have been proposed as synaptic memory device. All of above, RRAM is the most promising candidate, due to its several advantages, low power consumption, simple structure, excellent endurance, high operation speed. However, the desirable characteristic of synaptic device is different from traditional RRAM. It requires analog switching behavior and multi-level conductance states, which are beneficial to learning accuracy. In this thesis, the bipolar resistive switching behavior and synaptic characteristics are investigated in TiOx-based synaptic memory device. There are three parts in this thesis. First, different thickness TiOx film are deposited in TiN/Ti/TiOx/TiN structure. The relationship between thickness and electrical characteristics is discussed. The thickness of the TiOx switching layer determine the working operation current of the devices. The thicker layer device can work at lower compliance current and make smaller conductive filament. In addition, the influence of different pulse amplitudes applied on potentiation and depression is investigated. When lower pulse amplitude was applied on the device, conductance can gradually change and the nonlinearity is better. However, dynamic range become small and noise increase. The second part is that different Ti thickness effect on TiOx-based synaptic device. We compare their electrical characteristics and synaptic characteristics. We observed that the analog behavior can be improved after inserting a thin Ti layer. Different thickness of Ti layer make different thickness of interfacial layer, which leads the TiOx- based memory device has different capability to form and rupture the filament. As a result, they perform different electrical characteristics and weight update behavior. The other part is that comparing ZrOx/TiOx synaptic device and TiOx synaptic device. The ZrOx/TiOx synaptic device shows more stable analog switching and the nonlinearity of potentiation and depression can be improved to 2.08 and 1.84. Furthermore, it exhibits good endurance and data retention properties.It demonstrates good performance not only for data storage application but also for mimicking biological synapse.